เสียงที่ใช้ร่วมกัน

Many Japanese toilets include a button called 'Otohime' — literally 'Sound Princess.' It plays the sound of flushing water while you're still sitting, so no one outside can hear anything. It was invented in the 1980s after researchers found that Japanese women were flushing repeatedly just to mask sounds — wasting up to 20 liters of water per visit.